JPH0222006B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a fine silicate having a sharp particle size distribution and controllable particle size. Specifically, a specific metal salt is reacted with an alkali metal silicate while applying a strong shearing force,
In particular, it relates to a method for producing fine silicates useful as intermediates for silicic acid. Silicic acid is widely used as a filler for rubber and synthetic resins, as a matting agent for paints, and as a carrier for various drugs. The silicic acid used for such purposes is generally desired to have an ultra-fine average particle diameter of about several microns and an extremely sharp (narrow range) particle size distribution. As a result of intensive research in order to obtain the above-mentioned silicic acid, the present inventors have found that particle size can be controlled in a fine range by reacting a specific metal salt with an alkali metal silicate while applying a strong shearing force. ,
The present inventors have discovered that a silicate having an extremely sharp particle size distribution, which is particularly useful as an intermediate for silicic acid, can be obtained, and the present invention has been provided. That is, the present invention provides an alkali metal silicate with a water-soluble metal salt containing at least one metal selected from Group A, Group B, and Group metals of the periodic table.
This is a method for producing silicate, which is characterized by carrying out the reaction in an aqueous medium while applying a strong shearing force. According to the present invention, ultrafine silicate with a particle size of 1 to several μm and a sharp particle size distribution can be obtained by simply crushing the produced silicate after filtration and drying without any special crushing or classification. be able to. Therefore, by treating the ultrafine silicic acid with acid,
Silicic acid that can be used for the above-mentioned purposes can be easily obtained. The alkali metal silicate of the present invention is sodium silicate, potassium silicate, lithium silicate, or a mixture thereof, and is generally used as an aqueous solution. Among them, sodium silicate is economically advantageous and is used industrially. The concentration of the alkali metal silicate is 0.17 to 1.7 mol/SiO ₂ , preferably
0.5 to 1.5 mol/mole is used. SiO ₂ concentrations lower than the above range are not economical and
If it is higher than 1.7 mol/mol, the particle size of the produced silicate may become large and the particle size distribution may become broad, which is not preferable. Also, the molar ratio of alkali metal to silicic acid in the alkali metal silicate used: SiO ₂ /R ₂ O
(R = alkali metal: Na, K, Li, etc.) is generally 1 to 3.4, and in particular when the method of the present invention is carried out using 1.5 to 3.3, the average particle size of the obtained product is extremely small. preferable. If SiO ₂ /R ₂ O is lower than 1, the average particle size of the produced silicate will be large and the particle size distribution will be broad (wide range), which is undesirable. However, it is not practical. In the present invention, when controlling the average particle size of silicate, the molar ratio of SiO ₂ /R ₂ O is changed, or SiO ₂
This can be easily done by controlling the concentration of. The metal salts used in the present invention are hydrochloric acid, sulfuric acid, nitric acid, etc., as well as various organic or inorganic acids. , and a metal consisting of at least one of Group (Fe, Ni, etc.) metals,
The metal salt is soluble in water. Examples of these metal salts include magnesium chloride, calcium chloride, aluminum chloride, iron chloride, magnesium sulfate, calcium sulfate, aluminum sulfate, iron sulfate, magnesium nitrate, and calcium acetate. Among them, chlorides and sulfates of calcium, magnesium, and aluminum are preferably used because particle size can be easily controlled during silicate synthesis. Moreover, especially when a magnesium salt is used, silicic acid with a large specific surface can be obtained after acid treatment. The concentration of the metal salt may be determined by the concentration of R ₂ O (R: alkali metal) in the alkali metal silicate. Generally, M/R ₂ O (M: equivalent of water-soluble metal salt, R: alkali metal) is 1 to 2, preferably 1.0 to 1.3, and if it is lower than this range, silicate formation will be insufficient. However, it is not economical to add too much. In the present invention, a method is generally used in which the above-mentioned alkali metal silicate and water-soluble metal salt are reacted in the presence of an aqueous medium in a reaction tank, and the reaction slurry is extracted. In this case, a known method is adopted for the reaction operation, but a preferred method is to add the alkali metal silicate and the water-soluble metal salt simultaneously at the same rate into the reaction tank to cause the reaction, and to make the reaction solution equal to the amount added. This is a continuous method in which raw materials are supplied and reaction products are withdrawn at the same time. At this time, the average residence time of the reaction solution in the reaction tank may be appropriately selected depending on the reaction rate, capacity, etc., but generally it is only about several tens of minutes; if it is too short, the average particle size of the silicate slurry produced It is not economical if the length is not uniform or is too long. The most important thing in the present invention is to perform the reaction while applying a strong shearing force to the solution in the reaction tank. The shearing force referred to here is the shearing stress that acts on the fluid when it passes through a narrow channel at high speed. Equipment that applies shearing force include the homomixer and homoline chimiser (Tokushu Kika Kogyo Co., Ltd.). Co., Ltd.), colloid mill, etc.
Any disperser that generates strong shearing force can be used without any restrictions. In the present invention, the intensity of shearing force during the reaction has a large effect on the particle size and particle size distribution of the silicate. That is, if the shearing force is weak, the average particle size will be large and the particle size distribution will also be broad, so it is important to adjust the number of rotations of the disperser, the clearance of the flow path, and the working time. Therefore, the strength of the shearing force applied when producing the silicate of the present invention varies depending on the model of the disperser, but in general, when the clearance is 0.5 mm and the linear velocity of the blade is 10 m/sec, it is practically From an economical point of view, it is preferable to choose a time in the range of 30 to 120 minutes. The concentration of the silicate slurry obtained as described above is generally 0.5 to 40% SiO ₂ , and the slurry has an ultrafine average particle size of 1 to 4 μm, with a sharp particle size distribution. The silicate slurry obtained as described above is filtered and washed with water to remove by-product salts using conventional methods, then dried using a device such as a spray dryer, and crushed and classified as necessary. Therefore, a silicate having an extremely small particle size and a sharp particle size distribution can be obtained. Examples will be shown below, but the present invention is not particularly limited to the following examples. Example 1 Homo mixer with internal volume 1 (Tokushu Kika Kogyo Co., Ltd.)
First, add 600 ml of water to a reaction tank equipped with a Then,
Sodium silicate (SiO ₂ 1.47 mol/, Na ₂ O 0.98 mol/, molar ratio SiO ₂ /Na ₂ O = 1.5) was mixed with a homomixer while applying a strong shearing force under the clearance and linear velocity as described above. Magnesium sulfate aqueous solution (MgSO ₄ 1.0 mol/, excess (equivalent ratio)
MgSO ₄ /Na ₂ O=1.02) were added at a rate of 10 ml/min each. At the same time, the reaction solution was withdrawn at a rate of 20 ml/min to obtain a magnesium silicate slurry.
The average residence time of the reaction solution at this time was 30 minutes.
The slurry concentration of magnesium silicate became almost constant from 1 hour after the start of the reaction, and coarse powder with an average particle size of 1.5 μm and a narrow particle size distribution with good sharpness was continuously obtained. This reaction slurry was filtered under reduced pressure and washed with water, and the resulting cake (83% water) was repulped in water to the same concentration as the reaction slurry, and then instantly dried with a spray dryer to form a slurry. A dried product with exactly the same particle size distribution was obtained. These average particle sizes are shown in FIG. 1 (Graph 1 and Graph 2). The particle size distribution was measured by Coulter counter method. In addition, the chemical analysis value of the dried product is MgO21.6%,
The SiO ₂ content was 69.3%, and the igloss (including attached moisture) was 9.1%. The composition of the magnesium silicate obtained from this result is considered to be MgO1.5Na ₂ OnH ₂ O. Comparative Example 1 Except that the homomixer in the reaction tank in Example 1 was replaced with a stirrer and the shear force during the reaction was omitted,
Everything was carried out as in Example 1. The average particle size of the reaction slurry was as large as 4.5μ, and the particle size distribution was also broad. The particle size distribution is shown in Figure 1 (Graph 3). Examples 2 to 8 All the same procedures as in Example 1 except that the sodium silicate and magnesium sulfate were combined with the alkali silicate and water-soluble metal salt shown in Table 1.
It was carried out as follows. The results are shown in FIGS. 2 and 3. 【table】

[Brief explanation of drawings]

1 to 3 show particle size distributions of silicates in slurries or dried silicates obtained in Examples and Comparative Examples. In FIG. 1, graph 1 (---○---) is magnesium silicate graph 2 (---×---) of the slurry after reaction in Example 1, and magnesium silicate graph 3 (---●---) after drying in Example 1. -) is magnesium silicate of the slurry after reaction in Comparative Example 1. In Fig. 2, graph 4 (---○---) is graph 5 (---△---) of magnesium silicate of the slurry after reaction in Example 2. is Magnesium silicate graph 6 (---●---) of the slurry after reaction in Example 3 is Calcium silicate graph 7 (---×---) of the slurry after reaction in Example 4 Calcium silicate of post-slurry In Fig. 3, graph 8 (---○---) is aluminum silicate graph 9 (---●---) of post-reaction slurry in Example 6. The aluminum silicate graph 10 (---x---) is the iron silicate of the slurry after the reaction in Example 8.

Claims (1)

[Scope of Claims] 1. A water-soluble metal salt containing at least one alkali metal silicate selected from Group A, Group B, and Group metals of the periodic table is subjected to strong shearing in an aqueous medium. A method for producing a silicate characterized by reacting while applying force. 2. The manufacturing method according to claim 1, wherein the alkali metal silicate is sodium silicate. 3 Molar ratio of alkali metal silicate SiO ₂ /R ₂ O
The manufacturing method according to claim 1, wherein (R: alkali metal) is 1.0 to 3.4. 4. The manufacturing method according to claim 1, wherein the water-soluble metal salt is at least one selected from magnesium chloride, magnesium sulfate, calcium chloride, calcium sulfate, aluminum chloride, and aluminum sulfate. 5. Claim 1, wherein the alkali metal silicate has an equivalent ratio M/R ₂ O of the alkali metal and water-soluble metal salt (M: equivalent of water-soluble metal salt, R: alkali metal) of 1.0 to 1.3. manufacturing method.